Various types and configurations of tachometers are presently known. One particular type of tachometer is implemented by mechanically coupling an electrical generator to the device whose rotation rate is being detected. With this configuration, the generator voltage is proportional to the device rotation rate. Other types of tachometers use an optical principle, in which an optical encoder disk or reflective marks on the device provide an optical indication of rotation that can be detected.
One advantage of the electrical generator configuration is that the generator may be used also as a power source. In this manner, a wireless tachometer may be made. However, the resultant device may be relatively large, since the combination of the generator and associated mechanical linkage to the device could occupy a relatively large volume. Furthermore, for large devices, such mechanical linkage can become relatively difficult to implement.
Hence, there is a need for a tachometer that can be implemented using a relatively simple coupling to a device, and/or in a relatively small volume. The present invention addresses at least these needs.